C-S and C-Se Bond Formation at Bridging Vinyliminium Ligands in Diiron Complexes

The vinyliminium complexes [Fe2{μ-η1:η3-C(R)C(R)CN-(Me)2}(μ-CO)(CO)(Cp)2][SO3CF3] (R = Me, 3a;R=CO2Me, 3b; R = Ph, 3c) were treated with S8 in the presence oftBuLi, undergoing fragmentation and affording the corresponding six-membered metallacyclic complexes [Fe(Cp)(CO){SC-(R)=C(R)C(NMe2)S}] (5a–c). Complexes 5a–c result from cleavage of the diiron precursor and addition of S to the vi-nyliminium ligand to generate a dithiochelating ligand. Analogous reactions of the vinyliminium complexes [Fe2{μ-η 1:η3-C(R)C(R)CN(Me)(Xyl)}(μ-CO)(CO)(Cp)2][SO3CF3](R= Me,3d; R=CO2Me,3e), which contain a Xyl group (Xyl = 2,6-Me2C6H3) in place of a methyl, displayed a different outcome. Complex3dafforded the diiron complex [Fe2{μ-η 1:η3-C(Me)=C(CS2)C=N(Me)(Xyl)}(μ-CO)(CO)(Cp)2](10), whereas3eled to the formation of the five-membered metalla-cycle [Fe(Cp)(CO){C{N(Me)(Xyl)}C(CO2Me)C(CO2Me)S}] (11) together with the diiron complex [Fe2{μ-η 1 :η 3 -C-(CO2Me)=C(S)C=N(Me)(Xyl)}(μ-CO)(CO)(Cp)2](12). The formation of 10 and 12 implies C–H and C–C cleavage, respectively, and C–S bond formation without rupture of the diiron framework. The vinyliminium complexes3a–dand also [Fe2{μ-η1:η3-C(Et)C(Et)CN(Me)(CH2Ph)}(μ-CO)(CO)-(Cp)2][SO3CF3](3f) reacted with gray selenium in the pres-ence of tBuLi to afford the five-membered metallacycles [Fe(Cp)(CO){C{N(Me)R}C(R)C(R)Se}] (R = R = Me,13a;R = Me, R =CO2Me,13b;R=Me, R = Ph,13c; R = Xyl, R = Me,13d;R=CH2Ph, R=Et,13f) in which one Se atom has been incorporated into the chelating ligand. The X-ray mo-lecular structures of 5a and13a have been determined.